Whether you’re a little kid jumping into the pool on your summer break or an adult reaping the benefits of swimming for health and longevity, swimming can be a fun and even relaxing way to work your body and mind.

Looking at competitive swimmers, it’s hard to miss their toned physiques and muscular arms and shoulders. Their aerobic capacities are tremendous, too, as they spend countless hours each week with their faces submerged in water between breaths.

With toned muscles and the cardiovascular capacity to compete in such an aerobically demanding sport, looking at lifelong and competitive swimmers begs the question: Does swimming build muscle or is it more of a cardio workout? We chatted with experts to find out.

Does swimming build muscle and strength?

Strength training has many benefits: building muscle, maintaining muscle mass, and creating strong and stable joints, to name a few.

Strength training is a high-resistance, low-impact activity. By lifting heavy objects without significant forces of impact acting on your body (like jumping or hopping), your body leverages its muscles to move the heavy objects, which is the essence of a strength workout.

As you work specific muscles—and nourish them with protein after a workout—you develop muscle tone and mass and overall muscular strength.

Swimming is also a high-resistance, low-impact activity. The activity provides a lot of force to push against in order to make progress (the force is the water in this case) without requiring you to enact tremendous amounts of impact on your body. In this way, swimming is an excellent form of resistance training, which is one of the reasons why people looking for a gentle yet efficient workout opt for it.

Colorado-based swim and triathlon coach and certified personal trainer KJ Kroetch, CPT, notes that while swimming does build muscle and strength, it builds swim-specific strength, which may or may not be applicable elsewhere in your life.

“Strength from swimming is really specific to the sport and may not always convert to other areas of life,” Kroetch says. “This is similar to any repetitive movement—not just swimming—where you’ll build specific strength to that movement. The bonus with swimming is that there are four strokes you can learn—freestyle, backstroke, breaststroke, and butterfly—and that means you have four ways to build swim-specific strength.”

The professional and Olympic swimmers you see on TV and social media have built some of their muscle mass from swimming alone, but swimmers of that level are supplementing their swim training with land-based strength and resistance training in a gym, according to Kroetch.

A small 2019 study in the International Journal of Environmental Research and Public Health¹ followed 34 women as they were divided into two groups: one that didn’t participate in any swim training over 12 weeks and one that participated in a 12-week, 36-session swim training program that had the women in that group swim a total of 42,000 meters over the 12 weeks.

While women in the swim training group saw a significant decrease in body fat of up to 9.5 percent over the 12 weeks, they didn’t see a huge boost in muscle mass—swimming only increased their muscle mass by a maximum of 2.1 percent.

This doesn’t mean that swimming isn’t good resistance training—but it reinforces Kroetch’s point that swimming is good strength training… for swimming. Repeating a movement many times over builds familiarity and movement-specific strength, which is the case with the motions of any of the four swim strokes.

Swim equipment to build strength

To increase how much resistance you experience during a swim workout, you can use a variety of swim equipment—and many pools may even have this equipment on hand at their pool decks.

Julie Dunkle, a California-based triathlon coach and accomplished triathlete and open water swimmer, is an advocate of using swim equipment properly to help boost the strength benefits of a pool workout.

1. Hand paddles

“Swim paddles are a fantastic tool for increasing upper-body strength,” Dunkle says. “They increase the surface area of your hands, creating more resistance as you pull through the water.”

When using hand paddles ($20, Amazon), maintain proper technique. Consider removing the wrist strap and using only a finger strap to identify any flaws in your stroke as you pull your forearm and upper arm through the water.

2. Pull buoy 

“A pull buoy, which is placed between the upper thighs, isolates your upper body by keeping your legs buoyant,” Dunkle explains. “This allows you to focus solely on your arm strokes without worrying about kicking or your legs in general.”

Use a pull buoy ($14, Amazon) with hand paddles to maximize emphasis on your upper body, enhancing arm strength.

3. Swim fins

“Standard swim fins, which go on your feet, are designed to enhance the kicking motion, primarily engaging the quadriceps,” Dunkle says. “This increased muscle engagement can significantly tax the cardiovascular system, making them beneficial for high heart rate training.”

Swim fins ($63, Amazon) also help refine kick technique and promote better body position in the water, according to Dunkle. They’re shorter and wider than standard snorkeling fins, which are long and narrow. They work by increasing resistance while kicking and helping build leg strength.

“You need to have strength in order to move through the water, and that muscular strength improves with repetition, but ultimately it’s your cardiovascular system that carries you through a swim workout.” —KJ Kroetch, CPT

Does swimming improve your cardiovascular system?

While swimming on its own can result in building swim-specific strength and potentially result in increased muscle mass, for many, the more noticeable athletic benefit of swimming is that it can improve your cardiovascular system and aerobic fitness.

A cardiovascular workout is generally one that requires continuous movement of your entire body through activities like cycling, running, power walking, or swimming.

Cardiovascular workouts often mean you are breathing—and your heart is pumping—faster than when you’re at rest. This is because when you’re participating in cardiovascular exercise, there’s an increased demand for oxygenated blood from your heart to be pumped to the rest of your body, according to the Mayo Clinic.

As you become fitter through cardio workouts, your body becomes more efficient at transporting oxygenated blood to your large muscle groups, which among other things, can allow you to hit faster paces or harder aerobic efforts.

“Swimming is more effective at building cardiovascular capabilities than building muscle—swimming is a low-impact activity, but that doesn’t mean it’s an easy activity cardiovascularly,” Kroetch says. “However, for most people, the cardiovascular demands of swimming are less strenuous on the body overall than a similar aerobic activity like running, which means you can spend more time in a productive heart rate zone while swimming, which helps you to build a strong base of aerobic fitness.”

During a massive multi-decade study called the Aerobics Center Longitudinal Study², which ran from 1974 to 2002, 46,000 people  were assessed over many years on their aerobic fitness and physical health as a result of their fitness activities. Swimmers and runners were the two “fittest” groups during the multi-year check ins, with the lowest blood pressure, cholesterol levels, and maximum energy output numbers, among other measures of cardiovascular health.

“Just like with other cardiovascular training, you can tailor swim workouts to make an impact on all heart rate zones of your cardiovascular fitness,” Kroetch says. “Longer but easier swims will help you to build an aerobic base, while harder efforts with short rest will improve your aerobic threshold.”

If you’re looking for a great cardio workout, you don’t always have to hit the treadmill. Swimming is an excellent way to improve cardiovascular fitness when done regularly for weeks at a time, or when coupled with other cardiovascular activities such as running.

Swimming workouts

Most standard lap pools are 25 yards or 25 meters from one end to the other, but check with your local lap pool to understand its length. The workout below is for yards or meters.

Incorporate at least 30 seconds of rest in between each interval; take more rest if needed.

A swimming workout to build strength

• 200 freestyle swim, no equipment
• 2×100 backstroke or breaststroke, no equipment
• 100 breaststroke, no equipment
• Using a kickboard and fins on your feet if they’re available:
• Using hand paddles and a buoy between your legs:
• 100 easy freestyle, no equipment
• 100 easy backstroke or breaststroke, no equipment

A swimming workout to improve your cardio

• 200 freestyle swim
• 2×100 backstroke or breaststroke
• 100 breaststroke
• 4×25 any stroke, increase your effort each 25, last 25 should leave you out of breath
• *take extra rest here until your breathing returns to normal*
• 4×25 any stroke, increase your effort each 25, last 25 should leave you out of breath
• 100 easy freestyle
• 4×100 freestyle, try to do the second 50 of each 100 faster than the first 50
• 100 easy backstroke
• 4×25 any stroke, each one a hard effort with plenty of rest
• 4×25 any stroke, start with a hard effort, each one gets easier
• 100 easy freestyle or backstroke

The bottom line

First and foremost, swimming is cardio. As a secondary benefit, swimming is resistance and strength training—but the strength you gain from swimming alone will best help you further your swimming and may not apply to other areas of your life or activities.

“Swimming exists at the intersection of a Venn diagram, where it feels quite resistance-based because you’re constantly working against the water, but swimming at its core is a cardiovascular exercise,” Kroetch says. “You need to have strength in order to move through the water, and that muscular strength improves with repetition, but ultimately it’s your cardiovascular system that carries you through a swim workout.”

Plus, swimming is the only sport where you can’t breathe any time you want to—you must time your breath when you rotate your body to place your face out of the water for a brief moment, Kroetch notes.

If you’re looking to add swimming to your workout regimen, Kroetch has some tips.

“Knowing how to swim as an activity and knowing how to swim laps at a lap pool aren’t necessarily the same thing,” Kroetch says. “It may be tempting to go to a lap pool and jump in with a plan to swim for 30 minutes straight, but that may be harder than you think, so I recommend starting with shorter repeats, or intervals, at an easier intensity.”

Once you’ve built up confidence, cardiovascular fitness, and strength from swimming laps, you can progress your swim workouts to increased intervals and decreased rest periods between the intervals.

Kroetch recommends swimming laps two-to-three times per week to see steady improvement in both cardiovascular and swim-specific strength capabilities.